Flexible Power Control for Extending Operating Range of PV–Battery Hybrid Cascaded H-Bridge Converters Under Unbalanced Power Conditions

Abstract

Due to the nonuniform solar irradiance, different temperature and inconsistent module features, the output power among each photovoltaic (PV) module in a single-phase cascaded H-bridge (CHB) inverter is unequal. The H-bridge module with higher power generation faces the risk of overmodulation. To further extending the operating range of the CHB PV inverter under unity power factor condition, a battery module is connected with the system in series to form a PV-battery hybrid CHB converter in this paper. Meanwhile, the corresponding flexible power control strategy is proposed. The injected power of the battery module is controlled adaptively according to the maximum modulation index (MI) of all PV modules. With the proposed approach, all PV modules are free from overmodulation even with severe power imbalance and thus more energy are harvested. The effectiveness of the proposed control method is verified by experimental results.